Sorry, a better example is: > data.frame(a=1)[FALSE] NULL data frame with 1 rows > data.frame(a=1)[NULL] NULL data frame with 1 rows
vs > data.frame()[FALSE] Warning in is.na(nm) : is.na() applied to non-(list or vector) NULL data frame with 0 rows > data.frame()[NULL] Warning in is.na(nm) : is.na() applied to non-(list or vector) NULL data frame with 0 rows Hadley ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
